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F3049_C44U_RADIAL • 9/20/2016

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Aluminum Can Power Film Capacitors

C44U Series, 600 – 1,300 VDC, for DC Link

Sealing

Hermetically Sealed Capacitors

When the temperature increases, the pressure inside the capacitor increases. If the internal pressure is high enough, it can

cause a breach in the capacitor which can result in leakage, impregnation, filling fluid or moisture susceptibility.

Resin Encased/Wrap & Fill Capacitors

The resin seals on resin encased and wrap and fill capacitors will withstand short-term exposure to high humidity

environments without degradation. Resins and plastic tapes will form a pseudo-impervious barrier to humidity and

chemicals. These case materials are somewhat porous and through osmosis can cause contaminants to enter the capacitor.

The second area of contaminated absorption is the lead-wire/resin interface. Since resins cannot bond 100% to tinned wires,

there can be a path formed up to the lead wire into the capacitor section. Aqueous cleaning of circuit boards can aggravate

this condition.

Barometric Pressure

The altitude at which hermetically sealed capacitors are operated controls the voltage rating of the capacitor. As the

barometric pressure decreases, the susceptibility to terminal arc-over increases. Non-hermetic capacitors can be affected

by internal stresses due to pressure changes. This can be in the form of capacitance changes or dielectric arc-over as well

as low insulation resistance. Heat transfer can also be affected by altitude operation. Heat generated in operation cannot be

dissipated properly and can result in high RI2 losses and eventual failure.

Radiation

Radiation capabilities of capacitors must be taken into consideration. Electrical degradation in the form of dielectric

embitterment can take place causing shorts or opens.